GAL and seminoma: We stratified the TCGA dataset of 156 samples into a seminoma expression signature (SOX17, PRAME, PRDM1 positive; SOX2, DNMT3B, GAL negative) and an EC expression signature (SOX2, DNMT3B, GAL positive; SOX17, PRAME, PRDM1 negative) (Supplementary Fig. S1C).